Methods and devices for auto-calibrating light dimmers

ABSTRACT

An automated dimming load controller automatically measures the relationship between the current draw and the dimmer setting for each light or group of lights connected to the load controller. Once measured, the relationship between the current draw and the dimmer setting can be used to enable the dimmer controller to adjust the lights between their minimum and maximum effective illumination. This automatic setting of the dimmer controller may be performed regularly to accommodate changes in performance or replacement of any of the connected lights, drivers or ballasts.

FIELD OF THE INVENTIONS

The inventions described below relate to the field of electrical powercontrollers for dimming electrical lights.

BACKGROUND OF THE INVENTIONS

Low voltage light drivers and ballasts do not have identicalrelationships between an applied dimming signal and the power drawn bythe combination of the driver/ballast and the connected lights.Consequently, replacing a driver/ballast with a comparable part willresult in different dimming performance making it time consuming toreplace a driver/ballast and reconfigure the system to obtain optimaldimmer performance.

This situation is complicated by the fact that low voltage light driversand ballasts have different non-linear relationships between the applieddimming signal and the power drawn by the combination of thedriver/ballast and the connected lights. In some cases the low end ofthe driver's dimming range may be at about 1VDC output of the 0-10Voutput range from a dimmer controller. Similarly, the high end of thedriver's dimming range may be at about 8.6VDC of the 0-10V output rangeof the dimmer controller. In this example, the dimming range between 0and 1VDC and from 8.6VDC and 10VDC is known as dead travel.

Determination of ballast or driver performance to guarantee the 1-100%dimmer position values match with the maximum and minimum power outputof a particular driver/ballast are typically accomplished by eye or viaa light meter. The operation is inaccurate and must be performedmanually. This is time consuming for an installer. This performancematching is also limited to the ballast/driver and the lights it iscombined with. All ballasts and drivers are not identical and afterinstallation, replacement of a light will destroy any correspondencebetween the light performance and the dimmer control setting.

SUMMARY

The devices and methods described below provide for a automaticmeasurement of the voltage and current relationships (power) for eachlight or group of lights connected to the dimmer controller andautomatic calibration of the dimmer controller to minimize dead travelat the low end, the high end or both ends of the dimmer settings. Oncemeasured, the relationship between the power draw and the dimmer settingcan be used to enable the dimmer controller to adjust the lights betweentheir minimum and maximum effective power draw. The automaticcalibration of the dimmer controller may be performed regularly toaccommodate changes in performance or replacement of any of theconnected lights, drivers or ballasts.

Lighting ballasts for fluorescent lamps and solid-state light driverseach provide a datasheet that indicates the curve of the wattage/dimmerpercent output relationship and often also the wattage/lumen outputrelationship. Specifically, at a given lumen output level as apercentage of maximum, the ballast or driver will draw power that isproportionally similar; i.e. at 50% dimming level the ballast or driverwill generally draw 50% of maximum power. A programmable dimmercontroller with an integrated light power measurement module asdescribed below runs a self-calibration to characterize theballast/driver system in conjunction with its particular light or lightsand determine the relationship of the wattage/dimmed output percentagerelationship automatically or on demand; either of which being moreaccurate and more time efficient than the current process. Theself-calibration algorithm may be performed over time to continue toadapt the dimmer controller's performance to any degradation that mayoccur to the connected ballasts or drivers over time.

A programmable dimmer controller is provided with a built-in powermeasurement module that measures power delivered to the light andmeasures and sets a programmable high and low trim value to establishthe effective dimming range. An algorithm within the software orfirmware of the programmable dimmer controller performs theself-calibration by applying changing power to the dimming outputs whilerecording the changes in energy usage thus establishing the relationshipbetween current delivered to the light and the dimmed output as apercentage of total.

The automated dimmer controller described below includes a dimmercontroller, a current measurement module for measuring current appliedto dimmable lights, a microprocessor operably connected between thedimmer controller and the current measurement module, a memory operablyconnected to the microprocessor and an algorithm stored in the memory toenable the microprocessor to calibrate the dimmer controller.

The method of automatically calibrating a dimmer controller connected toone or more lights described below includes the steps of automaticallyexercising one or more lights by varying the dimmer controller andmeasuring current drawn by the one or more lights, recording a dimmerminimum setting and a current minimum value as the low trim settings, adimmer maximum setting and a current maximum value as the high trimsettings and using the dimmer minimum setting, the current minimumvalue, the dimmer maximum setting and the current maximum value tocontrol the one or more lights. The determination of the high trimsettings and the low trim settings may be performed in any suitableorder and the determination of either the high or low trim settings maybe optional.

The method of automatically calibrating the dimmer controller asdescribed below includes the steps of selecting one or more lights to beexercised by the application of varying voltage and measuring currentdrawn by the one or more lights and setting the dimmer setting to 0% forthe selected lights. Measuring the current drawn by the selected lights,recording the current drawn as a ballast current minimum, increasing thedimmer setting by a selected amount, measuring the current drawn by theselected lights and determining if the measured current is greater thanthe ballast current minimum. If the measured current is within atolerance value of the ballast current minimum, recording the dimmersetting as a dimmer minimum and then returning to the step of increasingthe dimmer setting by a selected amount. If the measured currentincreases beyond the tolerance value of the current, recording thedimmer minimum as the final dimmer minimum and the current minimum asthe final current minimum. The final dimmer minimum and the finalcurrent minimum correspond to the low trim values for the dimmercontroller. The high trim values are determined by recording themeasured current as a ballast current maximum and the dimmer setting asballast dimmer maximum and increasing the dimmer setting by the selectedamount, measuring the current drawn by the selected lights anddetermining if the measured current is greater than the ballast currentmaximum. If the measured current increases beyond a tolerance value ofthe ballast current maximum, recording the dimmer setting as a ballastdimmer maximum and the measured current as the ballast current maximumand then returning to the step of increasing the dimmer setting by theselected amount. If the measured current is within the tolerance valueof the current maximum, recording the ballast dimmer maximum as thefinal dimmer maximum and the ballast current maximum as the finalcurrent maximum. The final dimmer maximum and the final current maximumrepresent the high trim values for the dimmer controller. The dimming ofthe selected lights is accomplished by the dimmer controller using thefinal dimmer minimum, the final current minimum, the final dimmermaximum and the final current maximum values (the high and low trimvalues).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a space equipped with an automateddimming load controller and a variety of lights.

FIG. 2 is a cross section of a light.

FIG. 3 is the control algorithm for the automated dimming loadcontroller of FIG. 1 to measure and set the minimum and maximum limitsfor the light drivers or ballasts.

FIG. 4 is a block diagram of a current measurement module connected to adimmer controller, a microprocessor and a variety of lights.

FIG. 5 is a block diagram of a dimming load controller with anintegrated current measurement module and a microprocessor controlling avariety of lights.

DETAILED DESCRIPTION OF THE INVENTIONS

FIG. 1 illustrates space 1 equipped with an automated dimmable lightingcontroller 2 and a variety of lights, sensors and controls such asswitch 6. Lights such as first light 3, second light 4 and third light 5may be individual lights such as second light 4 or third light 5, orthey may be multiple individual lights commonly controlled as a zone orother suitable combination of lights such as first light 3 which is zone7 comprising individual lights 8, 9 and 10.

Each light, such as lights 4, 5, 8, 9 and 10, is a combination of alight driver or ballast combined with one or more illumination elementsas illustrated in FIG. 2. For example, light 8 includes driver 8Aoperatively connected to one or more illumination elements such asillumination elements 8X and light 4 includes ballast 4A andillumination elements 4X. Lighting controller 2 includes currentmeasurement module 13, dimmer controller 14, microprocessor 15 and oneor more instruction sets operatively available to microprocessor 15 suchas instruction set 16. Instructions such as instruction set 16 may beavailable in software or firmware.

Ballasts/drivers 8A, 9A and 10A for lights 8, 9 and 10 respectively, donot provide output current from 0-100% corresponding linearly to thedimming voltage applied. Consequently, a dimmer controller set toprovide 100 percent illumination at 10V may be providing 100 percentillumination at 8 or 9 volts. There may also be a similar dead travelzone at the low end of the dimming control range. To bringcorrespondence between the dimming control input and the performance ofthe light ballast or driver, lighting controller 2 performs dimmingaccuracy calibration according to algorithm 20 of FIG. 3. Theinstructions for algorithm 20 are included in instruction set 16 whichruns on microprocessor 15. Algorithm 20 generates a final ballast (ordriver) minimum value and a final ballast (or driver) maximum value. Thefinal ballast (or driver) minimum value corresponds to the low trimvalue for the dimmer controller. The final ballast (or driver) maximumvalue corresponds to the high trim value for the dimmer controller. Thefinal ballast minimum value and maximum value will be used by thecalibrated dimmer controller to accurately control the adjusted lightsfor lighting control strategies such as maximum output reduction ordemand response light shedding.

Algorithm 20 of FIG. 3 begins with lighting controller 2 isolating eachindividual light or zone of lights to be exercised depending on thelight configuration and optional step 19 to set current tolerances forthe measured current. Referring to FIGS. 1 and 3, in step 21 lightingcontroller 2 through dimmer control 14 applies power to one or morelights to be exercised such as second light 4 or a zone having multiplelights such as zone 7 with lights 8, 9 and 10. In step 22 lightingcontroller 2 sets dimmer control 14 for the selected light to 0% andcurrent measurement module 13 measures and records the current appliedto the light or group of lights as ballast minimum current 22M. In step23, lighting controller 2 sets dimmer control 14 to increase dimmingsetting 23M 1% or other appropriate interval, and current measurementmodule 13 measures the current applied to the light. In step 24microprocessor 15 compares the previously recorded ballast minimumcurrent 22M against the current measured in step 23. If the currentmeasured in step 23 is the same as recorded ballast minimum current 22M,dimmer setting 23M is recorded as ballast dimmer minimum at step 25 andthe algorithm returns to step 23.

The determination of equivalence may be accomplished with any suitabletolerance level such as equality tolerance setting or settings such assetting 18 of optional step 19. A suitable tolerance may be selected tobe between 1% and 10% of the last measured value and +/−5% of themeasured value may be a default tolerance setting. Measured currentvalues within +/− tolerance setting 18 of the current minimum areconsidered the same or equivalent. If the current measured in step 23 isgreater than recorded ballast minimum current 22M, at step 26 ballastminimum current 22M and dimmer setting 23M are recorded as final currentand dimmer minimums 22X and 23X respectively. (A current measurement isgreater than the ballast minimum current if it exceeds the value of theballast minimum current 22M plus tolerance setting 18.)

The following steps measure and record the final current maximum 22Y andfinal dimmer maximum 23Y which correspond to the high trim values forthe light and driver combination tested. At step 27 current measurementmodule measures current to the light and it is recorded as temporarycurrent maximum 22P and the dimmer setting is recorded as temporarydimmer maximum 23P. In step 28 lighting controller 2 raises dimmercontrol 14 for the selected light 1% and current measurement module 13measures the current applied to the light or group of lights. In step 29microprocessor 15 compares the previously temporary current maximum 22Pagainst the current measured in step 28. If the current measured in step28 is greater than recorded temporary current maximum 22P, the dimmersetting from step 28 and the current measured in step 28 are recorded instep 30 as temporary current maximum 22P and temporary dimmer maximum23P respectively and the algorithm returns to step 28. If the currentmeasured in step 28 is the same as recorded temporary current maximum22P, the temporary current maximum 22P and temporary dimmer maximum 23Pfrom step 30 are recorded in step 31 as final current maximum 22Y andfinal dimmer maximum 23Y and the algorithm is complete.

Once measured and recorded, lighting controller 2 is calibrated to usefinal current minimum 22X, final dimmer minimum 23X, final currentmaximum 22Y and final dimmer maximum 23Y to enable dimming control ofthe power applied to the lights from 0% dimming to 100% dimming. Thecontroller calibration performed by the algorithm of FIG. 3 may beperformed with any suitable frequency and at any suitable time of day.

Steps 21 through 26 of algorithm 20 measure and record the final currentminimum 22X and final dimmer minimum 23X which correspond to the lowtrim values for the light and driver combination tested. Steps 27through 31 of algorithm 20 measure and record the final current maximum22Y and final dimmer maximum 23Y which correspond to the high trimvalues for the light and driver combination tested. An alternatealgorithm similar to algorithm 20 may be operated to determine the hightrim values first and then the low trim values. Alternatively, only thelow trim values may be determined and used or only the high trim valuesmay be determined and used. The determination of the high and low trimvalues may also be performed from a 100% dimmer setting and lowering thedimmer setting at the appropriate steps, or starting at the 50% dimmersetting and moving up and down through the dimmer range to determine thehigh and low trim values.

The block diagram of FIG. 4 illustrates a current measurement module 40connected to a dimmer controller 41 through microprocessor 42 which isoperably connected to memory 43. Current measurement module 40 isoperably connected to a variety of lights such as the lights in zones 44and zones 46 through N. Each of the dimmable lights in a lighting zonesuch as zone 44 is an individual light such as dimmable lights 48, 49,50 and 51. Each of lights 48, 49, 50 and 51 has a removable ballast ordriver such as drivers 48A, 49A, 50A and 51A respectively. Currentmeasurement module 40 includes any suitable current measuring circuit orelement such as current transducer 52 or a current shunt circuit. Themeasurement of the current 53 measured by current transducer 52 iscommunicated to microprocessor 42 as current data 54. Dimmer controller41 transmits dimming settings such as dimming setting 55 to the lightsin the controlled zone and to microprocessor 42. Dimming setting 55controls the dimming status of individual lights and the lights inlighting zones such as lights 48, 49, 50 and 51 of lighting zone 44 asinstructed by a suitable control such as switch 56 and or microprocessor42.

In use, microprocessor 42 performs a calibration of dimmer controller 41and the individual connected lights or zone of lights such as zones 44and 46 through N. The calibration process is illustrated in algorithm 20of FIG. 3.

The block diagram of FIG. 5 illustrates an automated dimming loadcontroller 60 which includes current measurement module 61 connected toa dimmer controller 62 through microprocessor 63 which is operablyconnected to memory 64. Current measurement module 61 is operablyconnected to a variety of lights such as the lights in zones 65 andzones 67 through X. Each of the dimmable lights in a lighting zone suchas zone 65 is an individual light such as dimmable lights 69, 70, 71 and72. Each of lights 69, 70, 71 and 72 has a removable ballast such asballasts 69B, 70B, 71B and 72B respectively. Current measurement module61 includes any suitable current measuring circuit or element such as acurrent transducer or current shunt circuit 73. The measurement of thecurrent 74 measured by current shunt circuit 73 is applied tomicroprocessor 63 as current data 75. Dimmer controller 62 transmitsdimming settings such as dimming setting 76 to the lights in thecontrolled zone and to microprocessor 63. Dimming setting 76 controlsthe dimming status of individual lights and the lights in lighting zonessuch as lights 69, 70, 71 and 72 of lighting zone 65 as instructed bycontrol 77 and or microprocessor 63.

In use, microprocessor 63 performs a calibration of dimmer controller 62under instruction and control from individual connected lights or zoneof lights such as zones 65 and 67 through X. The calibration process isillustrated in algorithm 20 of FIG. 3.

Current measurement modules include inductive current measurement, shuntcurrent measurement or any other suitable method or device for measuringcurrent delivered to a light or a group of lights. The voltage appliedto a light or group of lights generally corresponds to the dimmingsetting of the controller.

The preferred embodiments of the devices and methods described withrelation to lights. For the purposes of this disclosure, “lights” can beany suitable light emitting element such as LEDs, OLEDs, or other solidstate implementation as well as incandescent, fluorescent, compactfluorescent, high-intensity discharge (HID), halogen, krypton or xenon.Any other suitable loads may also be used.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. Theelements of the various embodiments may be incorporated into each of theother species to obtain the benefits of those elements in combinationwith such other species, and the various beneficial features may beemployed in embodiments alone or in combination with each other. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

We claim:
 1. A method of automatically calibrating a lighting controllerfor controlling light assembly, said light assembly having a ballast anda dimmable light, comprising the steps of: providing an automatedlighting controller comprising: a dimmer controller having a dimmersetting; a current measurement module for measuring current applied tothe ballast of the light assembly; a microprocessor operably connectedbetween the dimmer controller and the current measurement module; amemory operably connected to the microprocessor; and an algorithm storedin the memory to enable the microprocessor to calibrate the dimmercontroller; selecting a light assembly to be exercised by theapplication of varying voltage and measuring current drawn by the lightassemblies; setting the dimmer setting to 0% for the selected lightassembly; measuring the current drawn by the selected light assembly;recording the current drawn as a ballast current minimum; increasing thedimmer setting by a selected amount; measuring the current drawn by theselected light assembly and determining if the measured current isgreater than the ballast current minimum; if the measured current iswithin a tolerance value of the ballast current minimum, recording thedimmer setting as a dimmer minimum and the returning to the step ofincreasing the dimmer setting by a selected amount; if the measuredcurrent increases beyond the tolerance value of the current, recordingthe dimmer minimum as the final dimmer minimum and the current minimumas the final current minimum; recording the measured current as aballast current maximum and the dimmer setting as ballast dimmermaximum; increasing the dimmer setting by the selected amount; measuringthe current drawn by the selected light assembly and determining if themeasured current is greater than the ballast current maximum; if themeasured current increases beyond a tolerance value of the ballastcurrent maximum, recording the dimmer setting as a ballast dimmermaximum and the measured current as the ballast current maximum and thenreturning to the step of increasing the dimmer setting by the selectedamount; if the measured current is within the tolerance value of thecurrent maximum, recording the ballast dimmer maximum as the finaldimmer maximum and the ballast current minimum as the final currentmaximum; and controlling the dimming of the selected light assemblyusing the final dimmer minimum, the final current minimum, the finaldimmer maximum and the final current maximum.
 2. The method of claim 1further comprising the step of setting a low current tolerance of theballast current minimum and using the low current tolerance to determineif the measured current is within or exceeds the low current toleranceof the ballast current minimum.
 3. The method of claim 1 furthercomprising the step of setting a high current tolerance of the ballastcurrent maximum and using the high current tolerance to determine if themeasured current is within or exceeds the high current tolerance of theballast current maximum.
 4. The method of claim 1 further comprising thestep of setting a high current tolerance and using the current toleranceto determine if the measured current is within or exceeds the currenttolerance of the ballast current minimum, or is within or exceeds thecurrent tolerance of the ballast current maximum.